GASTRIC ANALYSIS 159 



colorimetrically the H ion concentration of an N/ioo solution of hydrochloric acid 

 using tropaeolin OO as an indicator and of an N/ioo acetic acid using methyl 

 orange as an indicator. Note the great difference between the true acidities of 

 the two solutions. 



Titrate 10 c.c. portions of N/ioo hydrochloric acid and of N/ioo acetic acid 

 with N/ioo KOH using phenolphthalein as an indicator. Note that identical 

 results are obtained for the titratable acidities of the two. 



2. Determine colorimetrically the H ion concentration of an N/ioo KOH 

 solution using tropaeolin O as an indicator, and of an N/ioo ammonia solution 

 using phenolphthalein as an indicator. Note the results and then titrate 10 c.c. 

 portions of both solutions with N/ioo HC1 using alizarin as an indicator. 



3. Mix equal portions of M/is potassium dihydrogen phosphate and M/i$ 

 disodium phosphate (see chart). Note that the mixture is practically neutral to 

 litmus. Titrate one 10 c.c. portion of this mixture with N/io KOH, using phe- 

 nolphthalein as an indicator. Titrate another portion with N/io HC1 solution, 

 using methyl orange as an indicator. 



4. Mix equal volumes of N/5 sodium acetate solution and N/5 acetic acid. 

 Note that the mixture is acid to litmus. Titrate one 10 c.c. portion with N/io 

 HC1 using tropaeolin OO as an indicator. Titrate another portion with N/io 

 KOH using phenolphthalein as an indicator. 



THE FRACTIONAL METHOD OF GASTRIC ANALYSIS 



Procedure in Gastric Analysis by the Fractional Method 



1. Introduction of the stomach tube (see pages 159 and 160). 



2. Removal of the residuum (see pages 160 and 161). 



3. Feeding the test meal (see page 161). 



4. Feeding the retention meal (in special cases), see page 161. 



5. Removing samples of stomach contents for analysis (see page 161) . 



6. Examination of the samples for: 



(a) Total acidity (see page 162). 



(b) Free acidity (see page 164). 



(c) Pepsin (see page 165). 



(d) Trypsin (not a routine procedure), see page 169. 



(e) Lactic acid (see page 170). 

 (/) Occult blood (see page 171). 

 (g) Bile (see page 17.1). 



(ti) Microscopical constituents (see page 173). 

 i. Introduction of the Stomach Tube. Whereas the large tube is 

 directly inserted by propulsion, the Rehfuss tube is swallowed in the 

 natural manner and aided by gravity. The tube may be passed in one 

 of three ways, i.e. : (i) lubricated; (2) with aid of fluid; (3) after throat is 

 cocainized. When passed by the first method the tip of the tube, after 

 thorough lubrication with glycerol or liquid petrolatum, is seized between 



